In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and also more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing, using a polishing apparatus, while a polishing liquid (slurry) containing abrasive particles such as silica (SiO2) or ceria (CeO2) therein is supplied onto a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing pad, so that the substrate is polished.
Improvement in the yield and enhancement in the operating rate of equipment are important issues for a semiconductor device manufacturing process including a CMP process. Therefore, a system such as EES (Equipment Engineering System) or FDC (Fault Detection & Classification) has been introduced in a fabrication plant (Fab) to monitor the operational situation of semiconductor manufacturing equipment, thereby preventing a lowering of the yield. In the case of a CMP apparatus, processing point data on a polishing table, a polishing head (top ring), a slurry, a dresser, and the like are reported to the FDC system in the fabrication plant (Fab), and the FDC system collects and analyzes such data to monitor variation in the data. Depending on the variation, the CMP apparatus receives a command to interrupt processing (FDC error) from the FDC system. The processing interruption command is, for example, a command to immediately terminate polishing of a wafer which is being processed in a first polishing step, and to return the wafer to a cassette without applying the wafer to a second polishing step and the following steps, i.e., with skipping the subsequent process steps. Further, other unprocessed wafers in the cassette also are treated as skipped wafers and become processing-completed wafers. These wafers are reported as “rejected” or “skipped” to the FDC system in the fabrication plant (Fab).
There is a demand in these days to rescue such wafers, whose processing have been terminated by a processing interruption command, by performing reprocessing of the wafers as much as possible. In the CMP apparatus, a wafer is subjected to a multi-stage polishing process in a plurality of chambers, and thus a reprocessing process for a wafer differs significantly depending on the process step in which processing of the wafer is interrupted, i.e., depending on whether processing of the wafer is interrupted in a first polishing step, in a second polishing step, or in a cleaning step after the polishing process. It is therefore necessary for the reprocessing of the wafer to customize the recipe depending on the interrupted case. However, the apparatus is remotely controlled online by a host computer in the fabrication plant (Fab). As a general rule, a single recipe is provided for a wafer cassette. Therefore, in order to assign a new recipe for reprocessing after interruption, it is necessary to carry a wafer carrier out of the apparatus, carry the wafer carrier again into the apparatus and re-register the recipe. In this case, a waiting time for the carrying-in of the wafer carrier again becomes a loss of time before the start of reprocessing, and there are many non-rescuable cases.